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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">trace</span></code> — Trace or track Python statement execution</a><ul>
<li><a class="reference internal" href="#command-line-usage">Command-Line Usage</a><ul>
<li><a class="reference internal" href="#main-options">Main options</a></li>
<li><a class="reference internal" href="#modifiers">Modifiers</a></li>
<li><a class="reference internal" href="#filters">Filters</a></li>
</ul>
</li>
<li><a class="reference internal" href="#programmatic-interface">Programmatic Interface</a></li>
</ul>
</li>
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  <div class="section" id="module-trace">
<span id="trace-trace-or-track-python-statement-execution"></span><h1><a class="reference internal" href="#module-trace" title="trace: Trace or track Python statement execution."><code class="xref py py-mod docutils literal notranslate"><span class="pre">trace</span></code></a> — Trace or track Python statement execution<a class="headerlink" href="#module-trace" title="Permalink to this headline">¶</a></h1>
<p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.8/Lib/trace.py">Lib/trace.py</a></p>
<hr class="docutils" />
<p>The <a class="reference internal" href="#module-trace" title="trace: Trace or track Python statement execution."><code class="xref py py-mod docutils literal notranslate"><span class="pre">trace</span></code></a> module allows you to trace program execution, generate
annotated statement coverage listings, print caller/callee relationships and
list functions executed during a program run.  It can be used in another program
or from the command line.</p>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<dt><a class="reference external" href="https://coverage.readthedocs.io/">Coverage.py</a></dt><dd><p>A popular third-party coverage tool that provides HTML
output along with advanced features such as branch coverage.</p>
</dd>
</dl>
</div>
<div class="section" id="command-line-usage">
<span id="trace-cli"></span><h2>Command-Line Usage<a class="headerlink" href="#command-line-usage" title="Permalink to this headline">¶</a></h2>
<p>The <a class="reference internal" href="#module-trace" title="trace: Trace or track Python statement execution."><code class="xref py py-mod docutils literal notranslate"><span class="pre">trace</span></code></a> module can be invoked from the command line.  It can be as
simple as</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">trace</span> <span class="o">--</span><span class="n">count</span> <span class="o">-</span><span class="n">C</span> <span class="o">.</span> <span class="n">somefile</span><span class="o">.</span><span class="n">py</span> <span class="o">...</span>
</pre></div>
</div>
<p>The above will execute <code class="file docutils literal notranslate"><span class="pre">somefile.py</span></code> and generate annotated listings of
all Python modules imported during the execution into the current directory.</p>
<dl class="cmdoption">
<dt id="cmdoption-trace-help">
<code class="sig-name descname">--help</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-help" title="Permalink to this definition">¶</a></dt>
<dd><p>Display usage and exit.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-version">
<code class="sig-name descname">--version</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-version" title="Permalink to this definition">¶</a></dt>
<dd><p>Display the version of the module and exit.</p>
</dd></dl>

<div class="versionadded">
<p><span class="versionmodified added">New in version 3.8: </span>Added <code class="docutils literal notranslate"><span class="pre">--module</span></code> option that allows to run an executable module.</p>
</div>
<div class="section" id="main-options">
<h3>Main options<a class="headerlink" href="#main-options" title="Permalink to this headline">¶</a></h3>
<p>At least one of the following options must be specified when invoking
<a class="reference internal" href="#module-trace" title="trace: Trace or track Python statement execution."><code class="xref py py-mod docutils literal notranslate"><span class="pre">trace</span></code></a>.  The <a class="reference internal" href="#cmdoption-trace-l"><code class="xref std std-option docutils literal notranslate"><span class="pre">--listfuncs</span></code></a> option is mutually exclusive with
the <a class="reference internal" href="#cmdoption-trace-t"><code class="xref std std-option docutils literal notranslate"><span class="pre">--trace</span></code></a> and <a class="reference internal" href="#cmdoption-trace-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">--count</span></code></a> options. When
<a class="reference internal" href="#cmdoption-trace-l"><code class="xref std std-option docutils literal notranslate"><span class="pre">--listfuncs</span></code></a> is provided, neither <a class="reference internal" href="#cmdoption-trace-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">--count</span></code></a> nor
<a class="reference internal" href="#cmdoption-trace-t"><code class="xref std std-option docutils literal notranslate"><span class="pre">--trace</span></code></a> are accepted, and vice versa.</p>
<dl class="cmdoption">
<dt id="cmdoption-trace-c">
<code class="sig-name descname">-c</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--count</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-c" title="Permalink to this definition">¶</a></dt>
<dd><p>Produce a set of annotated listing files upon program completion that shows
how many times each statement was executed.  See also
<a class="reference internal" href="#cmdoption-trace-coverdir"><code class="xref std std-option docutils literal notranslate"><span class="pre">--coverdir</span></code></a>, <a class="reference internal" href="#cmdoption-trace-f"><code class="xref std std-option docutils literal notranslate"><span class="pre">--file</span></code></a> and
<a class="reference internal" href="#cmdoption-trace-no-report"><code class="xref std std-option docutils literal notranslate"><span class="pre">--no-report</span></code></a> below.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-t">
<code class="sig-name descname">-t</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--trace</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-t" title="Permalink to this definition">¶</a></dt>
<dd><p>Display lines as they are executed.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-l">
<code class="sig-name descname">-l</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--listfuncs</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-l" title="Permalink to this definition">¶</a></dt>
<dd><p>Display the functions executed by running the program.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-r">
<code class="sig-name descname">-r</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--report</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-r" title="Permalink to this definition">¶</a></dt>
<dd><p>Produce an annotated list from an earlier program run that used the
<a class="reference internal" href="#cmdoption-trace-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">--count</span></code></a> and <a class="reference internal" href="#cmdoption-trace-f"><code class="xref std std-option docutils literal notranslate"><span class="pre">--file</span></code></a> option.  This does not
execute any code.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-trackcalls">
<code class="sig-name descname">-T</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--trackcalls</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-trackcalls" title="Permalink to this definition">¶</a></dt>
<dd><p>Display the calling relationships exposed by running the program.</p>
</dd></dl>

</div>
<div class="section" id="modifiers">
<h3>Modifiers<a class="headerlink" href="#modifiers" title="Permalink to this headline">¶</a></h3>
<dl class="cmdoption">
<dt id="cmdoption-trace-f">
<code class="sig-name descname">-f</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--file</code><code class="sig-prename descclassname">=&lt;file&gt;</code><a class="headerlink" href="#cmdoption-trace-f" title="Permalink to this definition">¶</a></dt>
<dd><p>Name of a file to accumulate counts over several tracing runs.  Should be
used with the <a class="reference internal" href="#cmdoption-trace-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">--count</span></code></a> option.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-coverdir">
<code class="sig-name descname">-C</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--coverdir</code><code class="sig-prename descclassname">=&lt;dir&gt;</code><a class="headerlink" href="#cmdoption-trace-coverdir" title="Permalink to this definition">¶</a></dt>
<dd><p>Directory where the report files go.  The coverage report for
<code class="docutils literal notranslate"><span class="pre">package.module</span></code> is written to file <code class="file docutils literal notranslate"><em><span class="pre">dir</span></em><span class="pre">/</span><em><span class="pre">package</span></em><span class="pre">/</span><em><span class="pre">module</span></em><span class="pre">.cover</span></code>.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-m">
<code class="sig-name descname">-m</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--missing</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-m" title="Permalink to this definition">¶</a></dt>
<dd><p>When generating annotated listings, mark lines which were not executed with
<code class="docutils literal notranslate"><span class="pre">&gt;&gt;&gt;&gt;&gt;&gt;</span></code>.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-s">
<code class="sig-name descname">-s</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--summary</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-s" title="Permalink to this definition">¶</a></dt>
<dd><p>When using <a class="reference internal" href="#cmdoption-trace-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">--count</span></code></a> or <a class="reference internal" href="#cmdoption-trace-r"><code class="xref std std-option docutils literal notranslate"><span class="pre">--report</span></code></a>, write a brief
summary to stdout for each file processed.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-no-report">
<code class="sig-name descname">-R</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--no-report</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-no-report" title="Permalink to this definition">¶</a></dt>
<dd><p>Do not generate annotated listings.  This is useful if you intend to make
several runs with <a class="reference internal" href="#cmdoption-trace-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">--count</span></code></a>, and then produce a single set of
annotated listings at the end.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-g">
<code class="sig-name descname">-g</code><code class="sig-prename descclassname"></code><code class="sig-prename descclassname">, </code><code class="sig-name descname">--timing</code><code class="sig-prename descclassname"></code><a class="headerlink" href="#cmdoption-trace-g" title="Permalink to this definition">¶</a></dt>
<dd><p>Prefix each line with the time since the program started.  Only used while
tracing.</p>
</dd></dl>

</div>
<div class="section" id="filters">
<h3>Filters<a class="headerlink" href="#filters" title="Permalink to this headline">¶</a></h3>
<p>These options may be repeated multiple times.</p>
<dl class="cmdoption">
<dt id="cmdoption-trace-ignore-module">
<code class="sig-name descname">--ignore-module</code><code class="sig-prename descclassname">=&lt;mod&gt;</code><a class="headerlink" href="#cmdoption-trace-ignore-module" title="Permalink to this definition">¶</a></dt>
<dd><p>Ignore each of the given module names and its submodules (if it is a
package).  The argument can be a list of names separated by a comma.</p>
</dd></dl>

<dl class="cmdoption">
<dt id="cmdoption-trace-ignore-dir">
<code class="sig-name descname">--ignore-dir</code><code class="sig-prename descclassname">=&lt;dir&gt;</code><a class="headerlink" href="#cmdoption-trace-ignore-dir" title="Permalink to this definition">¶</a></dt>
<dd><p>Ignore all modules and packages in the named directory and subdirectories.
The argument can be a list of directories separated by <a class="reference internal" href="os.html#os.pathsep" title="os.pathsep"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.pathsep</span></code></a>.</p>
</dd></dl>

</div>
</div>
<div class="section" id="programmatic-interface">
<span id="trace-api"></span><h2>Programmatic Interface<a class="headerlink" href="#programmatic-interface" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="trace.Trace">
<em class="property">class </em><code class="sig-prename descclassname">trace.</code><code class="sig-name descname">Trace</code><span class="sig-paren">(</span><em class="sig-param">count=1</em>, <em class="sig-param">trace=1</em>, <em class="sig-param">countfuncs=0</em>, <em class="sig-param">countcallers=0</em>, <em class="sig-param">ignoremods=()</em>, <em class="sig-param">ignoredirs=()</em>, <em class="sig-param">infile=None</em>, <em class="sig-param">outfile=None</em>, <em class="sig-param">timing=False</em><span class="sig-paren">)</span><a class="headerlink" href="#trace.Trace" title="Permalink to this definition">¶</a></dt>
<dd><p>Create an object to trace execution of a single statement or expression.  All
parameters are optional.  <em>count</em> enables counting of line numbers.  <em>trace</em>
enables line execution tracing.  <em>countfuncs</em> enables listing of the
functions called during the run.  <em>countcallers</em> enables call relationship
tracking.  <em>ignoremods</em> is a list of modules or packages to ignore.
<em>ignoredirs</em> is a list of directories whose modules or packages should be
ignored.  <em>infile</em> is the name of the file from which to read stored count
information.  <em>outfile</em> is the name of the file in which to write updated
count information.  <em>timing</em> enables a timestamp relative to when tracing was
started to be displayed.</p>
<dl class="method">
<dt id="trace.Trace.run">
<code class="sig-name descname">run</code><span class="sig-paren">(</span><em class="sig-param">cmd</em><span class="sig-paren">)</span><a class="headerlink" href="#trace.Trace.run" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the command and gather statistics from the execution with
the current tracing parameters.  <em>cmd</em> must be a string or code object,
suitable for passing into <a class="reference internal" href="functions.html#exec" title="exec"><code class="xref py py-func docutils literal notranslate"><span class="pre">exec()</span></code></a>.</p>
</dd></dl>

<dl class="method">
<dt id="trace.Trace.runctx">
<code class="sig-name descname">runctx</code><span class="sig-paren">(</span><em class="sig-param">cmd</em>, <em class="sig-param">globals=None</em>, <em class="sig-param">locals=None</em><span class="sig-paren">)</span><a class="headerlink" href="#trace.Trace.runctx" title="Permalink to this definition">¶</a></dt>
<dd><p>Execute the command and gather statistics from the execution with the
current tracing parameters, in the defined global and local
environments.  If not defined, <em>globals</em> and <em>locals</em> default to empty
dictionaries.</p>
</dd></dl>

<dl class="method">
<dt id="trace.Trace.runfunc">
<code class="sig-name descname">runfunc</code><span class="sig-paren">(</span><em class="sig-param">func</em>, <em class="sig-param">*args</em>, <em class="sig-param">**kwds</em><span class="sig-paren">)</span><a class="headerlink" href="#trace.Trace.runfunc" title="Permalink to this definition">¶</a></dt>
<dd><p>Call <em>func</em> with the given arguments under control of the <a class="reference internal" href="#trace.Trace" title="trace.Trace"><code class="xref py py-class docutils literal notranslate"><span class="pre">Trace</span></code></a>
object with the current tracing parameters.</p>
</dd></dl>

<dl class="method">
<dt id="trace.Trace.results">
<code class="sig-name descname">results</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#trace.Trace.results" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a <a class="reference internal" href="#trace.CoverageResults" title="trace.CoverageResults"><code class="xref py py-class docutils literal notranslate"><span class="pre">CoverageResults</span></code></a> object that contains the cumulative
results of all previous calls to <code class="docutils literal notranslate"><span class="pre">run</span></code>, <code class="docutils literal notranslate"><span class="pre">runctx</span></code> and <code class="docutils literal notranslate"><span class="pre">runfunc</span></code>
for the given <a class="reference internal" href="#trace.Trace" title="trace.Trace"><code class="xref py py-class docutils literal notranslate"><span class="pre">Trace</span></code></a> instance.  Does not reset the accumulated
trace results.</p>
</dd></dl>

</dd></dl>

<dl class="class">
<dt id="trace.CoverageResults">
<em class="property">class </em><code class="sig-prename descclassname">trace.</code><code class="sig-name descname">CoverageResults</code><a class="headerlink" href="#trace.CoverageResults" title="Permalink to this definition">¶</a></dt>
<dd><p>A container for coverage results, created by <a class="reference internal" href="#trace.Trace.results" title="trace.Trace.results"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Trace.results()</span></code></a>.  Should
not be created directly by the user.</p>
<dl class="method">
<dt id="trace.CoverageResults.update">
<code class="sig-name descname">update</code><span class="sig-paren">(</span><em class="sig-param">other</em><span class="sig-paren">)</span><a class="headerlink" href="#trace.CoverageResults.update" title="Permalink to this definition">¶</a></dt>
<dd><p>Merge in data from another <a class="reference internal" href="#trace.CoverageResults" title="trace.CoverageResults"><code class="xref py py-class docutils literal notranslate"><span class="pre">CoverageResults</span></code></a> object.</p>
</dd></dl>

<dl class="method">
<dt id="trace.CoverageResults.write_results">
<code class="sig-name descname">write_results</code><span class="sig-paren">(</span><em class="sig-param">show_missing=True</em>, <em class="sig-param">summary=False</em>, <em class="sig-param">coverdir=None</em><span class="sig-paren">)</span><a class="headerlink" href="#trace.CoverageResults.write_results" title="Permalink to this definition">¶</a></dt>
<dd><p>Write coverage results.  Set <em>show_missing</em> to show lines that had no
hits.  Set <em>summary</em> to include in the output the coverage summary per
module.  <em>coverdir</em> specifies the directory into which the coverage
result files will be output.  If <code class="docutils literal notranslate"><span class="pre">None</span></code>, the results for each source
file are placed in its directory.</p>
</dd></dl>

</dd></dl>

<p>A simple example demonstrating the use of the programmatic interface:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">import</span> <span class="nn">trace</span>

<span class="c1"># create a Trace object, telling it what to ignore, and whether to</span>
<span class="c1"># do tracing or line-counting or both.</span>
<span class="n">tracer</span> <span class="o">=</span> <span class="n">trace</span><span class="o">.</span><span class="n">Trace</span><span class="p">(</span>
    <span class="n">ignoredirs</span><span class="o">=</span><span class="p">[</span><span class="n">sys</span><span class="o">.</span><span class="n">prefix</span><span class="p">,</span> <span class="n">sys</span><span class="o">.</span><span class="n">exec_prefix</span><span class="p">],</span>
    <span class="n">trace</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span>
    <span class="n">count</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>

<span class="c1"># run the new command using the given tracer</span>
<span class="n">tracer</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="s1">&#39;main()&#39;</span><span class="p">)</span>

<span class="c1"># make a report, placing output in the current directory</span>
<span class="n">r</span> <span class="o">=</span> <span class="n">tracer</span><span class="o">.</span><span class="n">results</span><span class="p">()</span>
<span class="n">r</span><span class="o">.</span><span class="n">write_results</span><span class="p">(</span><span class="n">show_missing</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">coverdir</span><span class="o">=</span><span class="s2">&quot;.&quot;</span><span class="p">)</span>
</pre></div>
</div>
</div>
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<li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">trace</span></code> — Trace or track Python statement execution</a><ul>
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